Re: [PATCH net 0/2] vsock: don't allow half-closed socket in the host transports

Michael S. Tsirkin
2019-10-12T22:38:56Z

On Fri, Oct 11, 2019 at 04:34:57PM +0200, Stefano Garzarella wrote:
> On Fri, Oct 11, 2019 at 10:19:13AM -0400, Michael S. Tsirkin wrote:
> > On Fri, Oct 11, 2019 at 03:07:56PM +0200, Stefano Garzarella wrote:
> > > We are implementing a test suite for the VSOCK sockets and we discovered
> > > that vmci_transport never allowed half-closed socket on the host side.
> > >
> > > As Jorgen explained [1] this is due to the implementation of VMCI.
> > >
> > > Since we want to have the same behaviour across all transports, this
> > > series adds a section in the "Implementation notes" to exaplain this
> > > behaviour, and changes the vhost_transport to behave the same way.
> > >
> > > [1] https://patchwork.ozlabs.org/cover/847998/#1831400
> >
> > Half closed sockets are very useful, and lots of
> > applications use tricks to swap a vsock for a tcp socket,
> > which might as a result break.
>
> Got it!
>
> >
> > If VMCI really cares it can implement an ioctl to
> > allow applications to detect that half closed sockets aren't supported.
> >
> > It does not look like VMCI wants to bother (users do not read
> > kernel implementation notes) so it does not really care.
> > So why do we want to cripple other transports intentionally?
>
> The main reason is that we are developing the test suite and we noticed
> the miss match. Since we want to make sure that applications behave in
> the same way on different transports, we thought we would solve it that
> way.
>
> But what you are saying (also in the reply of the patches) is actually
> quite right. Not being publicized, applications do not expect this behavior,
> so please discard this series.
>
> My problem during the tests, was trying to figure out if half-closed
> sockets were supported or not, so as you say adding an IOCTL or maybe
> better a getsockopt() could solve the problem.
>
> What do you think?
>
> Thanks,
> Stefano

Sure, why not.